"The tools already exist to mount cyberattacks now and they will improve in coming years — but countermeasures will improve, too," the Pew report said.

Key themes among the experts who said an attack is imminent are: the Internet is an inviting target as a critical infrastructure for essential defense, energy, banking, and transportation systems; security generally is not the first concern of technology developers; and major cyberattacks already have happened.

Those who say a major cyberattack isn’t imminent counter that there is steady progress in security measures; the threat of retaliation will deter attacks; and cyberattack hype is an exaggeration by those who stand to benefit from an atmosphere of fear.